Plastisols are generally dispersions of organic polymers in plasticizers which gel on heating to relatively high temperatures and cure on cooling to form the plastigel. Today, the most widely used plastisols in practice by far predominantly contain finely powdered polyvinyl chloride, copolymers of vinyl chloride and, more recently, methacrylate copolymers or styrene copolymers. These finely powdered polymers are dispersed in a liquid plasticizer and form the paste-like plastisol. Corresponding plastisols are used for various applications. They are used, for example, as sealing compounds, for impregnating and coating substrates of textile materials, as cable insulations and as adhesives. In the automotive industry, plastisols are used for underbody protection, for sealing seams, for lining hoods, as vibration-damping materials or as adhesives. Depending on the particular application envisaged, the plastisols contain other additives in addition to the fine-particle polymer powders and the liquid plasticizers. These other additives include, for example, fillers, coupling agents, stabilizers, flow aids, water-absorbing substances, pigments or blowing agents.
The plasticizers used, or suitable for use, in plastisol technology may be classified according to various aspects, the clearest classification being based on the chemical product classes of the plasticizers, such as phthalates, epoxides, aliphatic dicarboxylic acid esters, phosphates, polyesters, special plasticizers, extenders (hydrocarbons, chlorinated hydrocarbons). Most industrially used plasticizers are chemically stable diesters and triesters of aromatic or aliphatic di- and tricarboxylic acids. In a few cases, non-ester-like compounds with a plasticizing effect are also used. Phthalic acid diesters are by far the most widely used, especially for PVC homopolymers and copolymers, because hitherto they have been inexpensively available in large quantities. According to H. K. Felger (Editor), Kunst-stoffhandbuch xe2x80x9cPolyvinylchloridxe2x80x9d, Vol. 2/1, 2nd Edition 1985, Chapter 6.7, the particularly inexpensive dioctyl phthalates (di-2-ethylhexyl phthalate or diisooctyl phthalate) have hitherto enjoyed a dominant market share. However, because they may possibly be harmful to health, considerable efforts are being made worldwide to replace them by other plasticizers. Other common phthalate plasticizers are the various isomeric diisononyl phthalates, diisodecyl phthalates and diundecyl phthalates. The phthalic acid esters of C8/C10 alcohols or C7/C11 alcohols are also frequently used. However, these plasticizers have become considerably more expensive than the dioctyl phthalates, especially in recent years. Although the aliphatic dicarboxylic acid esters, especially the diadipates, diazelates and disebacates, have excellent low-temperature properties, they are only used in special cases on account of their high price. The same applies to the phosphate plasticizers, to the polyester plasticizers and to the other special plasticizers such as, for example, esters of terephthalic acid, trimellitic acid, pyromellitic acid, citric acid and the alkyl sulfonic acid esters of phenol and cresol.
To reduce costs, the hitherto known extenders or secondary plasticizers, largely hydrocarbons, are only used in admixture with primary plasticizers. Unfortunately, on account of their high volatility and their adverse affect on compatibility, the hitherto known extender plasticizers can only be used to a very limited extent and are employed almost exclusively to reduce the viscosity the plastisol pastes in order to guarantee their sprayability, especially by the airless process.
Accordingly, the problem addressed by the present invention was to find substances which would be suitable as least as secondary plasticizers, which would be physiologically safe and which would be economically available in sufficient quantities. They would preferably be based on renewable materials.